Method for optimizing dynamic stroke in the self servo-write process

ABSTRACT

Methods in accordance with embodiments of the present invention can be applied to determine a width of a data stroke along a rotatable medium of a data storage device. In one embodiment, the width can be determined by measuring a distance from a marker zone edge of a template pattern to a ramp, and measuring a distance from the marker zone edge to an inner crash stop. A track layout can be determined based on the width of the data stroke.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This U.S. patent application incorporates by reference all of thefollowing co-pending applications:

U.S. patent application Ser. No. ______ entitled “Dynamic StrokeOptimization in the Self Servo-Write Process,” by Calfee, et al., filedJun. 17, 2004 (Docket No. PANA-01128US1).

U.S. Provisional Application No. 60/533,292 entitled “Method forOptimizing Track Spacing Across a Stroke,” by Gururangan, et al., filedDec. 30, 2003.

U.S. Provisional Application No. 60/533,454 entitled “System forOptimizing Track Spacing Across a Stroke,” by Gururangan, et al., filedDec. 30, 2003.

U.S. patent application Ser. No. 10/733,131 entitled “Methods toDetermine Gross and Fine Positioning on a Reference Surface of a Media,”by Richard M. Ehrlich et al., filed Dec. 10, 2003.

TECHNICAL FIELD

The present invention relates to methods to servowrite media for use indata storage devices, and systems for applying such methods.

BACKGROUND

A hard disk drive typically contains one or more disks clamped to arotatable spindle motor, at least one head for reading data from and/orwriting data to the surfaces of each disk, and an actuator utilizinglinear or rotary motion for positioning the head(s) over selected datatracks on the disk(s). The actuator positions the read/write head overthe surface of the disk as the spindle motor rotates and spins the disk.

As the head is loaded onto a disk, for example from a ramp, the servosystem determines the position of the head on the disk surface byreading servo wedges passing beneath the head. A first track identifiedby the servo system as the head unloads from the ramp is identified asan acquire track. A first user track can be assigned based on theposition of the acquire track, and can define an outer boundary of adata region. The acquire track is some small distance from the ramp, andfarther from the outer diameter of the disk than is optimal or desired,wasting otherwise usable space and requiring an increased track densityfor a given hard disk drive capacity.

BRIEF DESCRIPTION OF THE FIGURES

Details of embodiments of the present invention are explained with thehelp of the attached drawings in which:

FIG. 1 is an exploded view of an exemplary hard disk drive for applyingembodiments of the present invention;

FIG. 2 is a close-up view of a head suspension assembly used in the harddisk drive of FIG. 1, showing head, slider and suspension;

FIG. 3 is a perspective view of the motion of the rotary actuator ofFIG. 1 unloading the head from the disk;

FIG. 4 is a control schematic of a typical hard disk drive for applyinga method in accordance with one embodiment of the present invention;

FIG. 5 is a diagram showing an example of a data and servo format for adisk in the drive of FIG. 1;

FIG. 6 is a partial detailed view of a disk from the hard disk driveshown in FIG. 1 having a final servo pattern;

FIG. 7 is an illustration of a reference surface of a disk having atemplate pattern;

FIG. 8 illustrates a portion of FIG. 7 including a portion of amarker-zone in accordance with one embodiment of the present invention.

FIG. 9 is a side view of the head suspension assembly as the head isloaded onto the disk from the ramp;

FIG. 10A is an exemplary plot of a measurement of average bias force asa function of track number;

FIG. 10B is an exemplary plot of a measurement of automatic gain controlvalue as a function of track number;

FIG. 11 is a flowchart of a method in accordance with one embodiment ofthe present invention to determine the position of a ramp relative to anactuator;

FIG. 12 is a flowchart of a method in accordance with one embodiment ofthe present invention to determine the position of a crash stop relativeto an actuator; and

FIG. 13 is a flowchart of a method in accordance with one embodiment ofthe present invention to calculate a data region for a plurality ofdisks.

DETAILED DESCRIPTION

FIG. 1 is an exploded view of an exemplary hard disk drive 100 forapplying a method in accordance with one embodiment of the presentinvention. The hard disk drive 100 includes a housing 102 comprising ahousing base 104 and a housing cover 106. The housing base 104illustrated is a base casting, but in other embodiments a housing base104 can comprise separate components assembled prior to, or duringassembly of the hard disk drive 100. A disk 108 is attached to arotatable spindle motor 120, for example by clamping, and the spindlemotor 120 is connected with the housing base 104. The disk 108 can bemade of a light aluminum alloy, ceramic/glass or other suitablesubstrate, with magnetizable material deposited on one or both sides ofthe disk 108. The magnetic layer has tiny domains of magnetization forstoring data transferred through heads 114. In one embodiment, each head114 is a magnetic transducer adapted to read data from and write data tothe disk 108. The disk 108 can be rotated at a constant or varying ratetypically ranging from less than 3,600 to more than 15,000 RPM (speedsof 4,200 and 5,400 RPM are common in hard disk drives designed formobile devices such as laptop computers). The invention described hereinis equally applicable to technologies using other media, as for example,optical media. Further, the invention described herein is equallyapplicable to devices having any number of disks attached to the spindlemotor 120. In other embodiments, the head 114 includes a separate readelement and write element. For example, the separate read element can bea magneto-resistive head, also known as a MR head. It will be understoodthat multiple head 114 configurations can be used.

A rotary actuator 110 is pivotally mounted to the housing base 104 by abearing 112 and sweeps an arc between an inner diameter (ID) of the disk108 and a ramp 130 positioned near an outer diameter (OD) of the disk108. Attached to the housing 104 are upper and lower magnet returnplates 118 and at least one magnet that together form the stationaryportion of a voice coil motor (VCM). A voice coil 116 is mounted to therotary actuator 110 and positioned in an air gap of the VCM. The rotaryactuator 110 pivots about the bearing 112 when current is passed throughthe voice coil 116 and pivots in an opposite direction when the currentis reversed, allowing for precise positioning of the head 114 along theradius of the disk 108. Each side of a disk 108 can have an associatedhead 114, and the heads 114 are collectively coupled to the rotaryactuator 110 such that the heads 114 pivot in unison. The inventiondescribed herein is equally applicable to devices wherein the individualheads separately move some small distance relative to the actuator. Thistechnology is referred to as dual-stage actuation (DSA).

FIG. 2 details an example of a subassembly commonly referred to as ahead suspension assembly (HSA) 222 comprising the head 114 formed on aslider 228, which is further connected with a flexible suspension member(a suspension) 226. The suspension 226 can be connected with an arm 224which in one embodiment can be either integrally formed with a mount fora bearing 112 or separately attached to the mount. The head 114 can beformed on the slider 228 using a number of different techniques, forexample the head 114 and slider 228 can be manufactured on a single dieusing semiconductor processing (e.g. photolithography and reactive ionetching). Spinning of the disk(s) 120 increases air pressure between theslider 228 and the surface of the disk, creating a thin air bearing thatlifts the slider 228 (and consequently the head 114) off of the surfaceof the disk 108. A micro-gap of typically less than one micro-inch canbe maintained between the disk 108 and the head 114 in one embodiment.The suspension 226 can be bent or shaped to act as a spring such that aforce is applied to the disk 108 surface. The air bearing resists thespring force applied by the suspension 226, and the opposition of thespring force and the air bearing to one another allows the head 114 totrace the surface contour of the rotating disk 108—which is likely tohave minute warpage—without “crashing” against the disk 108 surface.When a head 114 “crashes,” the head 114 collides with the disk 108surface such that the head 114 and/or the disk 108 surface may bedamaged. As is well understood by those of ordinary skill in the art,not all heads ride an air bearing as described above.

Refinements in disk fabrication have enabled manufacturers to producedisks 108 having ultra-smooth surfaces. Electrostatic forces can causestiction between the slider 228 and the surface. If the speed ofrotation of the disk 108 slows such that the air bearing collapses, theslider 228 can contact and stick to the surface of the disk 108, causingcatastrophic failure of the hard disk drive 100. Stiction can cause thedisk 108 to abruptly lock in position or stiction can cause the slider228 to forcibly disconnect from the suspension 226. Thus, when the harddisk drive 100 is not in use and before rotation of the disks 108 isslowed and stopped (i.e., the disks 108 are “spun down”), the heads 114can be removed from close proximity to the disk 108 surface bypositioning the suspension 226 on a ramp 130 located either adjacent tothe disk 108 or just over the disk 108 surface. FIG. 3 illustratesmotion of the actuator 110 as the slider 228 is unloaded from the disk108 and as the suspension 226 is driven up the ramp 130. The actuator110 pivots from location 1, where the slider 228 is positioned over thedisk 108 surface, to location 2, where the slider 228 is positionedadjacent to the disk 108. The range of motion of the actuator 130 iscommonly referred to as a stroke. The stroke can be limited at an innerdiameter by an ID crash stop 131. The ID crash stop 131 limits the freetravel of the rotary actuator by acting as a physical block to a voicecoil holder 115 of the actuator 110. As shown, the ID crash stop 131 isa peg or protrusion which can be associated with the housing. However,in other embodiments the ID crash stop 131 can be arranged in some otherfashion, and/or can include some other device for limiting the rotationof the actuator 110. For example, in one embodiment, a tab can extendfrom the voice coil holder 115 or and can contact a peg or protrusionassociated with the housing. One of ordinary skill in the art canappreciate the different ways in which the stroke of the actuator 110can be blocked or limited.

The slider 228 is removed from close proximity with the disk 108 bypivoting the actuator 110 such that a lift tab 332 extending from thesuspension 226 contacts the ramp surface and slides up the ramp 130. Theposition along the ramp 130 where the lift tab 332 first contacts theramp 130 can be called the touch-point. As the lift tab 332 slides upthe ramp 130 from the touch-point, the ramp 130 opposes the spring forceof the suspension 226 and forces the slider 228 (and the head 114) awayfrom the disk 108 surface. The HSA 222 can continue its motion along thestroke by traveling up the grade portion of the ramp 130 to asubstantially flat portion that optionally can include a detent forcradling the lift tab 332. The slider 228 can be loaded back onto thedisk 120 after the disk spins up to a safe speed. In other embodiments,the suspension 226 contacts the ramp 130 at a location along thesuspension 226 between the slider 228 and the pivot point. Unloading theslider 228 from the disk 108 prevents sticking, and reduces a risk ofdamage from non-operating shock by suspending the slider 228 over asignificantly wide gap between the slider 228 and an opposing slider orsurface. In still other embodiments in accordance with the presentinvention, the hard disk drive 100 can include a ramp 130 positionednear the ID, rather than near the OD. In such embodiments, the slider228 is removed from close proximity with the disk 108 by pivoting theactuator 110 toward the ID such that the lift tab 332 (or suspension226) contacts the ramp surface and slides up the ramp 130. Such harddisk drives 100 can further include an OD crash stop which can beassociated with the housing, and can limit or block a pivoting movementof the actuator 110 at the OD. Methods in accordance with the presentinvention are equally applicable to such hard disk drives 100 having aramp 130 positioned near the ID, and optionally an OD crash stop.Systems and methods described below are described with reference toembodiments of hard disk drives 100 having a ramp 130 positioned nearthe OD and an ID crash stop; however, it will be understood by one ofordinary skill in the art that such embodiments can alternativelyinclude a hard disk drive 100 having a ramp 130 positioned near the ID,and optionally an OD crash stop, and that such embodiments are withinthe scope of the present invention.

It should be noted, the description herein of the disk surface passingunder or beneath the slider is intended to mean that portion of the disksurface that is in close proximity to the slider. It will be understoodthat when referred to as “beneath” or “under” the slider, the disksurface can be over, or adjacent to the slider in actual physicalrelation to the slider. Likewise, it will be understood that whenreferred to as “over” the disk surface, the slider can be beneath, oradjacent to the disk surface in physical relation to the disk surface.By extension, where the slider is beneath the disk surface, thesuspension travels down the ramp when the slider is separated from thedisk surface.

FIG. 4 is a control schematic for the exemplary hard disk drive 100 ofFIG. 1. A servo system for positioning the head 114 can comprise amicroprocessor 446 and a servo controller, the servo controller existingas circuitry within the hard disk drive 100 or as an algorithm residentin the microprocessor 446, or as a combination thereof. In otherembodiments, an independent servo controller can be used. The servosystem uses positioning data read by the head 114 from the disk 108 todetermine the position of the head 114 over the disk 108. When the servosystem receives a command to position a head 114 over a track, the servosystem determines an appropriate current to drive through the voice coil116 and commands a VCM driver 440 electrically connected with the voicecoil 116 to drive the current. The servo system can further include aspindle motor driver 442 to drive current through the spindle motor 120and rotate the disk(s) 108, and a disk controller 444 for receivinginformation from a host 452 and for controlling multiple disk functions.The host 452 can be any device, apparatus, or system capable ofutilizing the hard disk drive 100, such as a personal computer, Webserver, or consumer electronics device. An interface controller can beincluded for communicating with the host 452, or the interfacecontroller can be included in the disk controller 444. In otherembodiments, the servo controller, VCM driver 440, and spindle motordriver 442 can be integrated into a single application specificintegrated circuit (ASIC). One of ordinary skill in the art canappreciate the different means for controlling the spindle motor 120 andthe VCM.

A flexible circuit (not shown) is connected with the rotary actuator 110to supply current to the voice coil 116 and to provide electricalconnections to the heads 114, allowing write signals to be provided toeach head 114 and allowing electrical signals generated during readingto be delivered to pre-amplification circuitry (pre-amp) 448. Typically,the flexible circuit comprises a polyimide film carrying conductivecircuit traces connected at a stationary end with the lower housing 104and at a moving end to the rotary actuator 110. The disk controller 444provides user data to a read/write channel 450, which sends signals tothe pre-amp 448 to be written to the disk(s) 108. The disk controller444 can also send servo signals to the microprocessor 446, or the diskcontroller 444 can control the VCM and spindle motor drivers directly,for example where multi-rate control is used. The disk controller 444can include a memory controller for interfacing with buffer memory 456.In one embodiment, the buffer memory 456 can be dynamic random accessmemory (DRAM). The microprocessor 446 can include integrated memory(such as cache memory), or the microprocessor 446 can be electricallyconnected with external memory (for example, static random access memory(SRAM) 454 or alternatively DRAM).

When a slider is loaded onto a disk from a ramp, the servo system mustdetermine the position of the head along the stroke. The HSA is unstablewhen the slider is initially loaded due to suction forces and thetransition from the graded ramp to the disk. Once the slider stabilizesand an air bearing is established between the disk and the slider, thehead 114 can determine its position on the disk by reading servo wedgespassing beneath the head 114. After some criteria is met—e.g., the trackis measured on a predefined number of consecutive servo wedges—the headlocks onto a track. The track on which the head locks is called anacquire track.

The information stored on such a disk can be written in concentrictracks, extending from near the ID to near the OD, as shown in theexemplary disk of FIG. 5. In an embedded servo-type system, servoinformation can be written in servo wedges 560, and can be recorded ontracks 562 that can also contain data. Data tracks written to the disksurface can be formatted in radial zones. Radial zones radiating outwardfrom the ID can be written at progressively increased data frequenciesto take advantage of an increase in linear velocity of the disk surfacedirectly under a head in the respective radial zones. Increasing thedata frequencies increases the data stored on the disk surface over adisk formatted at a fixed frequency limited at the ID by a circumferenceof a track at the ID. In a system where the actuator arm rotates about apivot point such as a bearing, the servo wedges may not extend linearlyfrom the ID to the OD, but may be curved slightly in order to adjust forthe trajectory of the head as it sweeps across the disk.

FIG. 6 illustrates a portion of a servo pattern 670 within a servo wedge560. The servo pattern 670 includes information stored as regions ofmagnetization. For example, where the servo pattern 670 islongitudinally magnetized, grey blocks are magnetized to the left andwhite spaces are magnetized to the right, or vice-versa. Alternatively,where the servo pattern 670 is perpendicularly magnetized, grey blocksare magnetized up and white spaces are magnetized down, or vice-versa.In other embodiments, information can be stored as indicia other thanregions of magnetization (e.g., optical indicia). Servo patterns 670contained in each servo wedge are read by the head as the surface of thespinning disk passes under the head. The servo patterns 670 can includeinformation identifying a data field. For example, the servo pattern 670can include a servo address mark (SAM), track identification, an index,etc. The exemplary final servo pattern is a simplification of a typicalservo pattern. The servo information can be arranged in any order, andcan include many more transition pairs than are illustrated (forexample, the region containing track identification is truncated asshown, and commonly includes many more transition pairs than areillustrated). Further, additional information, such as partial orcomplete wedge number information, can be included in the final servopattern. One of ordinary skill in the art can appreciate the myriaddifferent arrangements of information that can be contained in a servopattern. Systems and method in accordance with embodiments of thepresent invention should not be construed as being limited in scope tothose examples provided herein.

Servo information often includes transition pairs called “servo bursts.”The servo bursts 672 can be positioned regularly about each track, suchthat when a data head reads the servo bursts 672, a relative position ofthe head can be determined that can be used to adjust the position ofthe head relative to the track. For each servo wedge, this relativeposition can be determined, in one example, as a function of the targetlocation, a track number read from the servo wedge, and the amplitudesor phases of the bursts 672, or a subset of those bursts 672. Theposition of a head or element, relative to the center of a target track,will be referred to herein as a position-error signal (PES).

For example, a centerline 676 for a given data track can be “defined”relative to a series of bursts, burst edges, or burst boundaries, suchas a burst boundary defined by the lower edge of A-burst and the upperedge of B-burst. The centerline 676 can also be defined by, or offsetrelative to, any function or combination of bursts or burst patterns.This can include, for example, a location at which the PES value is amaximum, a minimum, or a fraction or percentage thereof. Any locationrelative to a function of the bursts can be selected to define trackposition. For example, if a read head evenly straddles an A-burst and aB-burst, or portions thereof, then servo demodulation circuitry incommunication with the head can produce equal amplitude measurements forthe two bursts, as the portion of the signal coming from the A-burstabove the centerline 676 is approximately equal in amplitude to theportion coming from the B-burst below the centerline 676. The resultingcomputed PES can be zero if the radial location defined by theA-burst/B-burst (A/B) combination, or A/B boundary, is the center of adata track, or a track centerline 676. In such an embodiment, the radiallocation at which the PES value is zero can be referred to as anull-point. Null-points can be used in each servo wedge to define arelative position of a track. If the head is too far towards the outerdiameter of the disk, or above the centerline, then there will be agreater contribution from the A-burst that results in a more “negative”PES. Using the negative PES, the servo controller could direct the voicecoil motor to move the head toward the inner diameter of the disk andcloser to its desired position relative to the centerline. This can bedone for each set of burst edges defining the shape of that track aboutthe disk.

The PES scheme described above is one of many possible schemes forcombining the track number read from a servo wedge and the phases oramplitudes of the servo bursts. For example, U.S. Pat. No. 5,381,281 toShrinkle et al. describes a PES scheme including a quad-servo burstpattern having first, second, third, and fourth servo bursts distributedin a series along the length of a portion of the data sector such thatthe center point of each servo burst is offset from adjacent bursts by aradial distance equivalent to one-half of the data track width. Aquadrature-based track following algorithm applying a difference of sumsof servo burst pair read voltages can minimize track following errorswhere servo bursts are mispositioned relative to one another. Such ascheme can benefit from embodiments of the present invention, as canmany other track following schemes. The schemes described above are onlya few of many possible schemes for positioning the head. Hard diskdrives using most (if not all) possible PES schemes could benefit fromthe invention contained herein.

Servo patterns can be written to the disks prior to assembly of the harddisk drive 100 using a media writer. A stack of disks is loaded onto themedia writer and servo patterns are carefully written onto the surfaceof each disk, a time consuming and costly process. Alternatively, acommonly less time-consuming and less expensive method can includewriting servo patterns or template patterns on a reference surface of asingle blank disk to be used as a reference for self-servo writingunwritten (and written) surfaces of one or more disks of an assembledhard disk drive. In one such self-servo writing method, calledprinted-media self-servo writing (PM-SSW), a coarse magnetic templatepattern can be transferred to a single disk surface (a referencesurface) by magnetic printing. A magnetic printing station can be usedto magnetically print or otherwise transfer a template pattern using aknown transfer technique. One such transfer technique is described in“Printed Media Technology for an Effective and Inexpensive Servo TrackWriting of HDDs” by Ishida, et al. IEEE Transactions on Magnetics, Vol.37, No. 4, July 2001. A blank disk (the reference surface) is DC erasedalong the circumferential direction of the disk by rotating a permanentmagnet block on the disk surface. A template, or “master”, disk is thenaligned with the blank disk and the two disks are securely faced witheach other by evacuating the air between the two disk surfaces through acenter hole in the blank disk. An external DC field is applied again inthe same manner as in the DC erasing process, but with an oppositepolarity. A number of different transfer techniques exist, and one ofordinary skill in the art can appreciate the different methods fortransferring a template pattern to a reference surface.

FIG. 7 illustrates a reference surface having a magnetically printedtemplate pattern 780 usable for PM-SSW. The template pattern 780 cancomprise clocking and, optionally, radial position information. Thetemplate pattern 780 can be divided into a number of pattern wedgesequivalent to the number of servo wedges 560 intended for the finalservo pattern 670, and printed such that the pattern wedges 560 trace anarc approximately matching the arcing sweep of the head 114 from the IDto the OD as described above. In other embodiments, the template pattern780 can have fewer or more pattern wedges than intended servo wedges560. Further, the pattern wedges need not be printed having arc.

A completed and enclosed hard disk drive can be assembled with at leastone disk 108 having a reference surface, and optionally one or moreblank disks. The template pattern 780 is applied by the hard disk driveelectronics to self-write highly resolved product embedded servopatterns 670 onto storage surfaces of each disk 108, including thereference surface having the template pattern 780. When the at least onedisk 108 is removed from a magnetic printing station and connected witha spindle 120, a shift typically occurs between the axis of rotation andthe center of tracks of the template pattern 780. The shift isattributable to machining tolerances of the spindle and magneticprinting station, as well as other variables. The track followed by thehead 114 can be displaced laterally in a sinusoidal fashion relative tothe head 114 as the disk 108 rotates. This sinusoidal displacement istypically referred to as eccentricity. Firmware executed by the harddisk drive 100 and the hard disk drive electronics enable the head 114positioned over the reference surface to follow and read the templatepattern 780 and enable each of the heads 114 to write precise finalservo patterns 670 on each of the respective surfaces of each disk 108.The hard disk drive 100 can compensate for eccentricity, writing tracksthat are nominally concentric with the center of rotation of thespindle, or alternatively, having some built-in eccentricity as definedby the firmware, for example. A final servo pattern 670 can be writtento the reference surface in any sequence, i.e. prior to, subsequent to,or contemporaneously with writing final servo patterns on some or all ofthe other surfaces. The final servo patterns can be writtencontemporaneously to reduce servo write times, and the final servopatterns 670 can be written between pattern wedges of the templatepattern 780. The template pattern 780 is overwritten either during theself-servo writing process or by user data. For example during hard diskdrive 100 testing data is written to the data fields and read back totest the data fields.

FIG. 8 illustrates a template pattern 780 including pairs of pulses 882,and chevrons (“zig-bursts” 884 and “zag-bursts” 886). The pulse pairs882 provide timing information for writing servo patterns. For example,the pulse pairs 882 can describe a crude SAM or an index mark. Thechevrons 884,886 are incorporated into the template pattern 780 to helpidentify radial positioning. As shown, the zig-bursts 884 incorporate apositive chevron angle relative to the radial line, and the zag-bursts886 incorporate a negative chevron angle relative to the radial line. Inother embodiments of the template pattern 780, the chevrons 884,886 canbe inverted such that the zig-bursts 884 incorporate a negative chevronangle relative to the radial line, and the zag-bursts 886 incorporate apositive chevron angle relative to the radial line (such that the burstsshown in FIG. 8 form upside down “V”'s). A radial distance between twochevrons can be referred to as a chevron cycle. A portion of the chevroncycle passing beneath the head 114 is converted into radial positioninginformation. Each chevron cycle provides positioning information alongthe width of the chevron cycle w_(c), and cannot communicate absoluteradial position. The pulse pairs 882 can be multiple, and as showninclude six pulse pairs. In one embodiment, one or more of the pulsepairs 882 can be used as a marker-zone for gross positioning. Forexample, the fourth transition-pair (or “di-bit”—a combination of an upand a down) from left to right is written so that the di-bit abruptlydisappears at some radius from the center of the disk 108. At a radiuscloser to the center of the disk 108, the di-bit can abruptly reappearso that the pulse pair 888 is continued. The interruption in the radialcontinuity of the magnetized pulse pair 888 can be any length. Forexample, in one embodiment the interruption can be 200 μm, while inother embodiments the switch in magnetization can occur once such that asingle marker-zone edge can be encountered by the head 114 as in travelsradially along the stroke.

Traces 883 overlay the pulse pairs 882 in FIG. 8, and represent signalsdetected by the head 114 in the digital portion at different radialpositions along the stroke as the disk 108 passes beneath the head 114.Where the head 114 traverses all six pulse pairs 882, for example thetop portion of the pulse pairs 882 as illustrated, the digital detectioncircuitry detects a di-bit. Where the head 114 traverses five of thepulse pairs 882, for example along the bottom portion of the pulse pairs882 as illustrated, the digital circuitry detects a missing di-bit.Where the head 114 straddles a marker-zone edge, moving radially fromthe pulse pair 882 to the marker-zone the probability of detecting thedi-bit slowly decreases. Where the head 114 equally straddles thetransition in the digital pattern, the probability of detecting thedi-bit is roughly 50%. The template pattern, as shown in FIG. 8 anddescribed in detail above, is encoded using di-bit encoding. However, itshould be noted that the template pattern can be encoded using any ofseveral possible schemes. For example, template patterns for use inmethods and systems in accordance with embodiments of the presentinvention can be encoded using wide bi-phase digital encoding (alsoreferred to herein as Manchester encoding). Wide bi-phase digitalencoding is described in greater detail in U.S. Pat. No. 5,862,005 toLeis, et al., incorporated herein by reference. One of ordinary skill inthe art can appreciate the different schemes for encoding a templatepattern on a reference surface.

Most commonly-used servo demodulation systems determine the digitalcontent of a servo wedge signal by detecting either the presence orabsence of filtered signal pulses at specified times or by detecting thevalue of the filtered signal at specified times. The signal can befiltered through a low-pass filter, a high-pass filter, or a combinationof the two (i.e., a band-pass filter). The amplitude of the filteredsignal can be calculated and compared to a threshold. The threshold canvary with an average amplitude of the filtered signal in the vicinity.The location along the stroke where the amplitude no longer exceeds thethreshold can be used as a crude position signal indicating amarker-zone edge. A radial position of the head 114 can be known withina distance that is smaller than the size of the read width of the head114 by detecting the marker-zone edge. The read width of the head 114 ismuch smaller than the width of the chevron cycle w_(c). For example, inone embodiment the width of the chevron cycle is 3 μm. The width of theread head 114 is a small fraction of a micron. Therefore, the chevronscan provide fractional positioning of the head 114 relative to the grosspositioning provided by the marker-zone edge.

A chevron cycle located at the same radial position as the marker-zoneedge can be assigned a designated cycle count from which the head 114can determine radial positioning along the stroke by the cycle count ofthe chevron over which the head 114 passes relative to the marker zoneedge. If the position of the head 114 is lost, the head 114 can locatethe marker-zone edge and the radial position is known to be thedesignated cycle count. For example, if the designated cycle count is1000, the radial position of the marker-zone edge is chevron cycle count1000 (plus a fractional cycle count based on whatever fractionalposition is measured from the actual chevron angle). Use of this schemecan present a problem if the location of the marker-zone edge nearlycoincides with an exact integer chevron cycle count. If one of thechevrons (either the zig-burst 884 or the zag-burst 886) has a phase ofvery nearly zero degrees at the edge of the marker-zone, then it can bedifficult to decide whether to set the integer portion of the chevroncycle count to the designated cycle count or one count less than thedesignated cycle count. Using the example discussed above, thedesignated cycle count for the zig-burst 884 at the marker-zone edge is1000, while the corresponding designated cycle count for the zag-burst886 is −1000. If the measured phase of the zig-burst 884 at themarker-zone edge is very near zero degrees, for the servo wedge at whichthe chevron cycle counts are altered to account for the known locationof the head 114, where the measured phase of the fractional cycle countis slightly more than zero degrees (i.e., a small positive phase) theinteger portion of the zig-burst 884 cycle count can be set to 1000,while where the measured phase of the fractional cycle count is slightlyless than 360 degrees (i.e., a small negative phase) the integer portionof the zig-burst 884 cycle count can be set to 999. Thus, a phase of afractional cycle count near zero degrees (but slightly greater) willresult in a total zig-burst 884 cycle count that is slightly greaterthan 1000, while a phase of a fractional cycle count near to 360 degrees(but slightly less) will result in a total zig-burst 884 cycle countthat is slightly less than 1000. The same reasoning can be applied todetermine the integer portion of the zag-burst 886 cycle count at thetime that both the zig-burst 884 and zag-burst 886 cycle counts arealtered to account for the known location of the head 114.

The marker-zone can be positioned anywhere along the stroke. In oneembodiment, the marker-zone can be positioned centrally along the datastroke (wherein the data stroke is that portion of the stroke traversingdata tracks), bisecting the data stroke and minimizing the maximumdistance from any location on the disk to the marker-zone, therebyimproving nominal recovery time where the head 114 slips chevron cycles.In other embodiments, the marker-zone can span a defined distance andhave a first edge, for example, near the OD and a second edge near theID. One of ordinary skill in the art can appreciate the myriad differentarrangements of the marker-zone on the disk.

Referring to FIG. 9, as a slider 228 is loaded onto a disk 108 from aramp 130, the slider 228 can contact the disk 108 surface. Contact cancause damage to one or both of the disk 108 surface and the slider 228.Such damage can interfere with the ability of a head connected with theslider to read from or write data to the disk. For example, debris ordamage on the disk surface can alter the surface so that an air gapformed between the slider and the surface is non-uniform, causinginstability or an air gap height that results in a weakened measured orwritten signal. A first user track 992 typically (though notnecessarily) contains critical system information and can be assigned toa track located some distance closer to the ID than the average acquiretrack. The distance between the first user track 992 and the averageacquire track 990 is an outer guard band OG that acts as a buffer sothat the head 114 can avoid reading or writing to the disk 108 whiletraversing a portion of the disk 108 surface possibly damaged bysporadic contact during frequent loading of the slider 228 from the ramp130 to the disk 108. The average acquire track 990 estimates thelocation of the touch-point 934 of the lift tab 332 for purposes ofsetting the first user track 992. Ideally, the touch-point 934 ispositioned in close proximity to the average acquire track 990 so that amaximum amount of the stroke is usable for storing user data. However,more likely the acquire track 990 is some small distance from the ramp130, and farther from the OD than is optimal or desired. Therefore, thebuffer is likely farther from the OD than is necessary, to avoiddefects.

The data stroke traverses a portion of the disk surface between thefirst user track 992 and a final user track 994 offset from the ID crashstop 131 by an inner guard band IG. In low-cost designs, the mechanicaltolerance of the ID crash stop 131 location and the touch-point 934location is a significant portion of the data stroke. The location ofthe average acquire track 990 from the touch-point 934 includes atolerance that can vary with the criteria for assigning an averageacquire track 990; therefore, setting the first user track 992 based onthe average acquire track 990 can further reduce the width of the datastroke (and increase the variability). Further, the first user track 992is typically assigned to a track that is a conservative distance fromthe average acquire track 990. Typically, a manufacturer will increasethe density of the tracks written to the disk 108 surface to produce ahard disk drive 100 having a targeted capacity. An increase in trackdensity can negatively impact hard disk drive 100 performance,resulting, for example, in a reduction in manufacturing tolerance forthe width of the head 114, or a degradation in the performance of theservo system.

The touch-point 934 can be more accurately located for defining afirst-user track 992 by detecting a dramatic change in an average biasforce as the actuator 110 contacts the ramp 130. Electrical bias forcescan result from voltage and current offsets in the electrical circuitryand can act on a rotary actuator 110 as a function of the radialposition of the head 114 on the disk 108. An average bias force can bemeasured by the servo system as the head 114 reads servo wedges passingbeneath the head 114. The servo system can seek the OD and measure theaverage control effort (i.e. bias force) required as the head 114changes radial position. FIG. 10A is a sample plot of average bias forceas a function of track number, where the origin represents the OD(rather than a first user track) and an increase in track numberindicates nearness to the ID. As the head 114 is pivoted toward the ODfrom the ID (moving from right to left on the plot), the average biasforce initially drops, and then gradually and steadily increases. Wherethe lift tab 332 contacts the ramp 130, a dramatic drop in average biasforce can be measured. In other embodiments, the bias force canincrease, rather than decrease. The measured bias is a function of thesum of multiple variables (e.g., flex circuit spring force, windage,etc.), and the multiple variables can be affected by hard disk drivecomponent geometry, disk spin speed, etc. Therefore, the sum of themultiple variables can increase in some embodiments.

Alternatively, the touch-point 934 can be located by detecting adramatic change in a level of gain adjustment in an automatic gaincontrol (AGC) circuit associated with the read/write channel 450. TheAGC circuit adjusts the amplitude of a signal received from the currentpreamplifier 448 within desirable boundaries when converting an analogsignal into digital form. FIG. 10B is a sample plot of AGC level as afunction of track number, where the origin represents the OD (ratherthan a first user track) and an increase in track number indicatesnearness to the ID. As the head 114 is pivoted toward the OD from the ID(moving from right to left on the plot), the AGC level increases. Thesharp rise in AGC level corresponds roughly to a contact point betweenthe lift tab 332 and the ramp 130, and can be attributed, at least inpart, to loading force on the slider 228. As the lift tab 332 contactsthe ramp 130, the lift tab 332 is raised and lifts the suspension 226,which applies a smaller loading force on the slider 228, whichconsequently flies higher to re-balance the reduced suspension loadingwith the air-bearing force.

As described above, data tracks written to the disk surface can beformatted in radial zones. For example, the servo pattern of FIG. 5includes two radial zones, a first radial zone extending from the ID toapproximately the middle of the data stroke, and a second radial zoneextending from the first radial zone to the OD and having a datafrequency greater than the data frequency of the first radial zone. Inother embodiments, a servo pattern in accordance with the presentinvention can include more radial zones. For example, in someembodiments the servo pattern can have twenty or more radial zones. Theradial positions of these zones are preferably tightly controlled tomaximize the robustness of the data format. Thus, the mechanicaltolerances of the ID crash stop and ramp affect the layout of the finalservo pattern relative to a fixed radial zone position. For example,where the data frequency of the second radial zone is 1.5× the datafrequency of the first radial zone, a shift in the position of the firstuser track can affect the data storage capacity of the diskapproximately 1.5× as much as a shift in the position of the final usertrack.

A method in accordance with one embodiment of the present invention caninclude determining a final servo pattern to be written to one or moresurfaces of a disk during a self-servo write process. The method can beapplied to a reference surface having a template pattern, for example asshown in FIGS. 7 and 8. The position of a ramp relative to a markerzone, and the location of the ID crash stop relative to the marker zonecan be found and applied to maximize a data stroke for a given guardband while maintaining superior absolute radial data zone placement. Thetemplate pattern can be printed to a reference surface, written to thereference surface by a media writer, or otherwise transferred to thereference surface, and can include determining a marker zone located ata known radial position.

Referring to the flowchart of FIG. 11, if the HSA is positioned on theramp, the slider can be positioned over the reference surface of thedisk by loading the HSA from the ramp to the disk (Step 1100). Once theslider is positioned over the surface, a radial reference position ofone or more of the pattern wedges is located as described above, bydetecting a marker zone edge of the template pattern (Step 1102). Oncethe marker zone edge is located, the position of the ramp can bedetermined by pivoting the rotary actuator such that the slider movestoward the OD along the stroke. As the actuator pivots, the headmeasures the number of cycle counts between the marker zone edge and theramp. As the lift tab (or some other portion of the HSA) contacts theramp, the average bias force drops dramatically and detectably and/orthe AGC level rises suddenly, locating the ramp relative to the markerzone edge (Step 1104). Alternatively, a sudden change in some othermeasurable metric known to result from contact between the HSA and theramp, can indicate the location of the ramp.

The ID crash stop can be identified in a similar fashion. Referring tothe flowchart of FIG. 12, if the HSA is positioned on the ramp, theslider can be positioned over the reference surface of the disk byloading the HSA from the ramp to the disk (Step 1200). Once the slideris positioned over the surface, a radial reference position of one ormore of the pattern wedges is located as described above, by detecting amarker zone edge of the template pattern (Step 1202). Once the markerzone edge is located, the position of the ID crash stop can bedetermined by pivoting the rotary actuator such that the slider movestoward the ID along the stroke. As the actuator pivots, the headmeasures the number of cycle counts between the marker zone edge and theID crash stop. As rotary actuator contacts the ID crash stop, theaverage bias force rises dramatically and detectably, locating the IDcrash stop relative to the marker zone edge (Step 1204). Alternatively,a sudden change in some other measurable metric known to result fromcontact actuator and the ID crash stop can indicate the location of theID crash stop.

Once the ramp interference point and the ID crash stop interferencepoint have been determined, the mechanical deviation of the ramp and theID crash stop from a nominal radial position can be calculated. Themechanical deviation of the ID crash stop and the ramp interferencepoint can be used as manufacturing feedback data, and optionally used asfailure criteria. In one embodiment, statistical methods are applied tocalculate a distribution around a nominal value of radial position forthe ID crash stop interference point and ramp interference point. Forexample, in one embodiment a Gaussian distribution can be calculated anda deviation, e.g. 3 sigma, can be assigned as a failure criteria.Alternatively, a fixed value for a radial position can be assigned as afailure criteria. Assembled hard disk drives that fail one or both ofthe failure criteria for the ID crash stop and ramp interference pointscan be binned as lower capacity drives, discarded, or otherwisedispositioned. In other embodiments, a total value of the data stroke iscalculated from the ID crash stop and ramp interference points andcompared with a failure criteria calculated or determined for the datastroke. Multiple different criteria can be applied to reject hard diskdrives having data strokes too small to provide robust performance atthe targeted radial density.

If a hard disk drive falls within acceptable criteria, the radialpositions of the ID crash stop and ramp interference points can be usedto calculate the available data stroke. Referring to the flowchart ofFIG. 13, a percentage of the data stroke within each of the radial zonescan be determined based on the radial positions of the interferencepoints (Step 1300). The radial zones can be weighted by thecircumferential data capacity of the radial zone relative to theinnermost radial zone (Step 1302). The track density can then becalculated (or defined) and a track layout determined based on therequired capacity of the hard disk drive or the required track densityof the hard disk drive (Step 1304). A final servo pattern can be writtento the surface of the disk within the hard disk drive, taking advantageof the width of the data stroke (Step 1306). In one embodiment, thefinal servo pattern can be written so that a number of data tracks areaccurately placed at the appropriate radial locations according to asingle read/write format and radial density. This scheme assuresaccurate data frequency at the various radial data zones. The ID and ODguard-bands can be assured of a minimum width by the failure criteriafor the radial positions of the interference points. An increase in thewidth of the data stroke results in increased guard-band width,resulting in improved servo robustness at the edges of the data region.

In other embodiments, the final servo pattern can be written so that avariable number of data tracks are accurately placed at the appropriateradial locations, again, according to a single read/write format andradial density. This scheme also assures accurate data frequency at thevarious radial data zones, and a minimum ID and OD guard-width. However,an increase in the width of the data stroke results in an additionalnumber of data tracks, increasing the capacity of the disk. In this way,hard disk drives can be binned and sold according to capacity, oralternatively customized, having only a minimum capacity and a variablemaximum capacity.

In still other embodiments, a minimum ID and OD guard width can beassigned, based on a slider width, or some other criteria, and theremaining data stroke is used to write data tracks having a variableradial density to maximize robustness of the written data for a givencapacity. The density of the remaining data stroke is determined by theradial width of the remaining data stroke and the relative proportion ofthe remaining data stroke within the inner and outer radial zones. Forexample, where a data stroke of a disk in a first hard disk drive isshifted closer to the ID than a data stroke of a disk having the sameradial width in a second hard disk drive, the disk from the first harddisk drive will have a higher radial density. This is because the radialpositions of the radial zones are fixed; therefore the size of the innerradial zone, having a lower frequency than the outer radial zone,increases when the ID crash stop interference point shifts toward theID, while the size of the outer radial zone, conversely having a higherfrequency than the inner radial zone, increases when the crash stopinterference point shifts away from the ID and toward the OD.

Methods in accordance with the present invention can further be appliedto self servo write a plurality of disks or a plurality of disk surfacesconnected with a spindle motor. Where a plurality of heads are connectedwith the actuator, a position of the ramps can be determined relative toa marker zone edge by positioning the plurality of heads over therespective disk surfaces, locating the marker zone edge as describedabove, and pivoting the actuator toward the OD of the plurality of diskssurfaces until the actuator contacts at least one of the ramps. Ametric—e.g. an average bias force and/or AGC level—is measured by theheads as the actuator pivots until contact between at least one of aplurality of HSAs connected with the actuator and a corresponding rampis detected. In one embodiment, the plurality of heads are tied togethervia the head stack and move together on the actuator. The head closestto a corresponding ramp determines the ramp interference point common toall heads. The bias force will change while servoing on any head whenthe head nearest a corresponding ramp comes into contact. Once thecommon ramp interference point is determined relative to the marker zoneedge, the actuator can be pivoted toward the ID until the actuatorcontacts the ID crash stop. As described above, the number of cyclesbetween the common ramp interference point and the marker zone edge, andbetween the marker zone edge and the crash stop interference point canbe measured as the head travels across the reference surface. A finalservo pattern can be determined and written to the one or more surfacesof the disk(s) as described above.

In some embodiments, multiple surfaces can include printed referencepatterns. In such embodiments, a ramp interference point can bedetermined for each surface and corresponding head by measuring a metriconly from the head associated with the target surface. A final tracklayout can be determined for each of the multiple surfaces, and a finalservo pattern can be written to each of the multiple surfaces inaccordance with the final track layout. Such embodiments can provide anadvantage in optimizing track layout across the entire drive,particularly where the mechanical tolerance between relative headposition is large.

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many modifications andvariations will be apparent to one of ordinary skill in the relevantarts. The embodiments were chosen and described in order to best explainthe principles of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications that are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the claims and their equivalence.

1. A method to bin a rotatable medium having a template pattern in adata storage device, which data storage device including a ramp, a crashstop, and a head connected with an actuator, the method comprising:determining a width of a data stroke; and comparing the width of thedata stroke to one or more criteria.
 2. The method of claim 1, whereindetermining a width of a data stroke includes: determining a location ofa marker zone edge of the template pattern; determining a location ofthe ramp relative to the marker zone edge; determining a location of thecrash stop relative to the marker zone edge; and calculating the widthof the data stroke based on the location of the ramp and the location ofthe crash stop.
 3. The method of claim 2, wherein determining a locationof the ramp relative to the marker zone edge includes: positioning thehead over the marker zone edge; reading the template pattern with thehead; measuring a metric while reading the template pattern; adjustingthe actuator such that the head moves toward an outer edge of therotatable medium; detecting a severe change in the metric.
 4. The methodof claim 2, wherein determining a location of the ramp relative to themarker zone edge includes: positioning the head over the marker zoneedge; reading the template pattern with the head; measuring a metricwhile reading the template pattern; adjusting the actuator such that thehead moves toward an inner diameter of the rotatable medium; detecting asevere change in the metric.
 5. The method of claim 3, wherein themetric is a bias force.
 6. The method of claim 3, wherein the metric isan AGC level.
 7. The method of claim 5, wherein the severe change is asevere drop.
 8. The method of claim 6, wherein the severe change is asharp rise.
 9. The method of claim 2, wherein determining a location ofthe crash stop relative to the marker zone edge includes: positioning ahead connected with the actuator over the marker zone edge; reading thetemplate pattern with the head; measuring a metric while reading thetemplate pattern; adjusting the actuator such that the head moves towardan inner diameter of the rotatable medium; detecting a severe change inthe metric.
 10. The method of claim 2, wherein determining a location ofcrash stop relative to the marker zone edge includes: positioning a headconnected with the actuator over the marker zone edge; reading thetemplate pattern with the head; measuring a metric while reading thetemplate pattern; adjusting the actuator such that the head moves towardan outer edge of the rotatable medium; detecting a severe change in themetric.
 11. The method of claim 9, wherein the metric is a bias force.12. The method of claim 11, wherein the severe change is a sharp rise.13. The method of claim 2, wherein calculating the width based on thelocation of the ramp and the location of the inner diameter includes:determining one or more portions of the data stroke within one or moreradial zones; weighing the one or more portions by circumferentialdensity; and summing the weighted one or more portions.
 14. The methodof claim 1, wherein the criterion is one of maximum track capacity andminimum track density.
 15. A method to write a final servo pattern on arotatable medium having a template pattern in a data storage devicehaving a ramp, a crash stop, and a read/write head connected with anactuator, comprising: determining a width of a data stroke; and writingthe final servo pattern on the rotatable medium based on the width. 16.The method of claim 15, wherein determining a width of a data strokeincludes: determining a location of a marker zone edge of the templatepattern; determining a location of a ramp relative to the marker zoneedge; determining a location of a crash stop relative to the marker zoneedge; and calculating the width based on the location of the ramp andthe location of the crash stop.
 17. The method of claim 16, whereindetermining a location of a ramp relative to the marker zone edgeincludes: positioning the head over the marker zone edge; reading thetemplate pattern with the head; measuring a metric while reading thetemplate pattern; adjusting the actuator such that the head moves towardan outer edge of the rotatable medium; and detecting a severe change inthe metric.
 18. The method of claim 16, wherein determining a locationof a ramp relative to the marker zone edge includes: positioning thehead over the marker zone edge; reading the template pattern with thehead; measuring a metric while reading the template pattern; adjustingthe actuator such that the head moves toward an inner diameter of therotatable medium; and detecting a severe change in the metric.
 19. Themethod of claim 17, wherein the metric is a bias force.
 20. The methodof claim 17, wherein the metric is an AGC level.
 21. The method of claim19, wherein the severe change is a severe drop.
 22. The method of claim19, wherein the severe change is a sharp rise.
 23. The method of claim20, wherein the severe change is a sharp rise.
 24. The method of claim16, wherein determining a location of crash stop ramp relative to themarker zone edge includes: positioning a head connected with theactuator over the marker zone edge; reading the template pattern withthe head; measuring a metric while reading the template pattern;adjusting the actuator such that the head moves toward an inner diameterof the rotatable medium; and detecting a severe change in the metric.25. The method of claim 16, wherein determining a location of crash stopramp relative to the marker zone edge includes: positioning a headconnected with the actuator over the marker zone edge; reading thetemplate pattern with the head; measuring a metric while reading thetemplate pattern; adjusting the actuator such that the head moves towardan outer edge of the rotatable medium; and detecting a severe change inthe metric.
 26. The method of claim 24, wherein the metric is a biasforce.
 27. The method of claim 26, wherein the severe change is a severedrop.
 28. The method of claim 26, wherein the severe change is a sharprise.
 29. The method of claim 16, wherein calculating the width based onthe location of the ramp and the location of the inner diameterincludes: determining one or more portions of the data stroke within oneor more radial zones; weighing the one or more portions bycircumferential density; and summing the weighted one or more portions.30. The method of claim 15, wherein writing the final servo pattern onthe rotatable medium based on the width includes: selecting a trackdensity; selecting a capacity; and determining a first user track and afinal user track based on the track density and the capacity; wherein adistance between the ramp and the first user track is at least a minimumouter guard band and a distance between the crash stop and the finaluser track is at least a minimum inner guard band.
 31. The method ofclaim 15, wherein writing the final servo pattern on the rotatablemedium based on the width includes: selecting an outer guard band;selecting an inner guard band; selecting a capacity; and determining atrack density based on the capacity, the outer guard band, the innerguard band, and the width.
 32. The method of claim 15, wherein writingthe final servo pattern on the rotatable medium based on the widthincludes: selecting an outer guard band; selecting an inner guard band;selecting a track density; and determining a capacity based on the trackdensity, the outer guard band, the inner guard band, and the width. 33.The method of claim 16, wherein determining a location of a ramprelative to the marker zone edge includes: locating the marker zone edgeusing the head; moving the actuator such that the head moves toward anouter edge of the rotatable medium; measuring a plurality of cycles asthe head moves from the marker zone edge toward an outer edge of therotatable medium; and determining a position of the ramp by detecting asevere change in the metric.
 34. The method of claim 16, whereindetermining a location of a crash stop relative to the marker zone edgeincludes: locating the marker zone edge using the head; moving theactuator such that the head moves toward an inner diameter of therotatable medium; measuring a plurality of cycles as the head moves fromthe marker zone edge toward the inner diameter of the rotatable medium;and determining a position of the crash stop by detecting a severechange in the metric.
 35. The method of claim 33, wherein the metric isa bias force.
 36. The method of claim 33, wherein the metric is an AGClevel.
 37. The method of claim 35, wherein the severe change is a severedrop.
 38. The method of claim 35, wherein the severe change is a sharprise.
 39. The method of claim 36, wherein the severe change is a sharprise.
 40. The method of claim 15, wherein the template pattern is one ofa media written pattern and a printed media pattern.
 41. The method ofclaim 30, wherein writing the final servo pattern on the rotatablemedium based on the width further includes writing a set of tracks fromthe first user track to the final user track.
 42. The method of claim31, wherein writing the final servo pattern on the rotatable mediumbased on the width further includes writing a set of tracks from thefirst user track to the final user track.
 43. The method of claim 32,wherein writing the final servo pattern on the rotatable medium based onthe width further includes writing a set of tracks from the first usertrack to the final user track.